It has been proposed to use a curable epoxy resin composition that contains a thermally conductive powder as a sealing or adhesive agent capable of efficiently transmitting heat generated by electronic components. However, since a cured body of such a composition has a high modulus of elasticity and is rigid, it was proposed to add an epoxy-containing organopolysiloxane (see Japanese Unexamined Patent Application Publication (hereinafter referred to as “Kokai”) H05-295084).
However, a curable epoxy resin composition that includes an epoxy-containing organopolysiloxane is still too rigid and does not provide the required stress reduction. Therefore, use of such a composition in conjunction with electronic components is limited because it causes warping of the electronic components and cracking of a cured body of the composition, whereby gaps may occur between the cured body of the composition and the electronic component.
It has been proposed to solve the above problem by preparing curable silicone compositions comprising epoxy-containing organopolysiloxanes and curing agents (see Kokai H05-320514, Kokai H07-53870 and Kokai 2005-154766). In order to form cured bodies with high thermal conductivity properties, such compositions normally contain a large amount of a thermally conductive metal powder, in particular, a silver powder. This increased the cost and specific gravity. On the other hand, in order to obtain a thermally conductive cured body and to reduce the production cost, it is possible to combine the composition with a thermally conductive nonmetal powder, a typical representative of which is alumina. However, the addition of alumina makes the composition too viscous and impairs handleability of the composition.
It is an object of the present invention to provide a curable silicone composition that, along with low viscosity, exhibits excellent industrial handleability and curability and that, when cured, forms a cured body that, along with flexibility and low specific gravity, possesses excellent thermal conductivity. It is another object to provide an electronic component that is sealed or adhesively bonded by means of a cured body of the aforementioned composition and that acquires high reliability.